Poly(3,4-ethylenedioxythiophene)

PEDOT possesses many advantageous properties compared to earlier conducting polythiophenes like 3-alkylthiophenes. For example, the polymer is optically transparent in its conducting state and has high stability, moderate band gap, and low redox potential.^[2][3] Its major disadvantage is its poor solubility, which is partly circumvented by use of composite materials such as PEDOT:PSS and PEDOT-TMA.

The polymer is generated by oxidation. The process begins with production of the radical cation of EDOT monomer, [C₂H₄O₂C₄H₂S]⁺. This cation adds to a neutral EDOT followed by deprotonation. The idealized conversion using peroxydisulfate is shown:

n C₂H₄O₂C₄H₂S + n (OSO₃)₂²⁻ → [C₂H₄O₂C₄S]_n + 2n HOSO₃⁻

Polymerization is usually conducted in the presence of polystyrene sulfonate (PSS), which acts as a template. PSS also provides a counter ion, which balances the charges in the reaction and hinders the formation of by-products such as 3,4-ethylenedioxy-2(5H)-thiophenone, and keeps the PEDOT monomers dispersed in water or aqueous solutions. ^[4] The resulting PEDOT:PSS composite can be deposited on a conductive support such as platinum, gold, glassy carbon, and indium tin oxide.^[5]

Applications of PEDOT include electrochromic displays and antistatics.^[6] PEDOT has also been proposed for photovoltaics, printed wiring, and sensors.^[6][4] PEDOT has been proposed for use in biocompatible interfaces.^[7][8]

Enhanced PEDOT's conductivity and surface area, making it a promising material for supercapacitors. Researchers at UCLA developed a nanofiber structure using a vapor-phase growth process, increasing its charge storage capacity nearly tenfold compared to conventional PEDOT. This new structure exhibited 100 times higher conductivity, a fourfold increase in surface area, and a charge storage capacity of 4600 mF/cm², while maintaining exceptional durability with over 70,000 charge cycles. These improvements enabled faster charging, greater efficiency, and longer lifespan, positioning PEDOT as a strong candidate for next-generation energy storage in renewable energy systems and electric vehicles.^[9]

• Bello, A.; Giannetto, M.; Mori, G.; Seeber, R.; Terzi, F.; Zanardi, C. (2007). "Optimization of the DPV Potential Waveform for Determination of Ascorbic Acid on PEDOT-Modified Electrodes". Sensors and Actuators B: Chemical. 121 (2): 430. doi:10.1016/j.snb.2006.04.066. hdl:11380/621556.
• Kumar, S. Senthil; Mathiyarasu, J.; Phani, K. L. N.; Yegnaraman, V. (2005). "Simultaneous Determination of Dopamine and Ascorbic Acid on Poly(3,4-ethylenedioxythiophene) Modified Glassy Carbon Electrode". Journal of Solid State Electrochemistry. 10 (11): 905. doi:10.1007/s10008-005-0041-7. S2CID 95645292.
• Zhang, Xinyu; MacDiarmid, Alan G.; Manohar, Sanjeev K. (2005). "Chemical Synthesis of PEDOT Nanofibers". Chemical Communications (42): 5328–30. doi:10.1039/b511290g. PMID 16244744.